so i have had this a few times. there are some things you can do if it happens.

1. check whether the charge is pending on your cc, and also whether it actually confirms in a few days time
2. try the "print/email e-ticket" option on mmb, but it may well error as noted in post 6
3. load the booking on the app and see if there is a ticket number shown
4. use the finnair site to email yourself your e-ticket https://www.finnair.com/gb-en/custom...ticket-receipt

if you do find you have an e-ticket via 3 and/or 4, i wouldn't do anything further. but if you cannot confirm there is an e-ticket, that is the point to contact ba and see what is going on.